DOHC

The DOHC-6 is PMI's most ambitious and highly advanced engineering and development project to date.  Developed out of a desire to improve the breathing performance of the cylinder head, the DOHC is intended to be a high-performance aluminum bolt-on head assembly.

The DOHC head begins as two separate 3.4 liter DOHC heads (GM’s LQ-1). Each head is cleaned, stripped and machined to become a perfectly matched set. Water jacket passages are closed off between the heads and then opened later during subsequent machining operations. The heads are welded together end-to end while installed on a fixture to maintain as much straightness and flatness as possible.

During the process, the head bolt hole bosses are re-machined for proper position for the Pontiac OHC block. Two “common” bolt bosses are welded closed, then plunge-cut on the mill, then sealed and re-bored though several weld-machine-weld-machine steps.

The cam carrier (stock items from the LQ-1 motor) go through a similar process of joining end to end, but are not welded, and have no water jackets to seal.

The end result is a 24 Valve DOHC head for the OHC block. Custom cam drive gearing is installed, as well as custom built cam shafts.

Designed and built to be a high-rpm, high horsepower screamer, these heads should only be used on “hardened” short blocks, where reconditioned rods and forged pistons have been installed.                                  

Image Gallery